Color Index The pigments used for artists’ colors are inorganic as well as organic. The inorganic pigments have been used since antiquity; most of them are extracted from minerals and soil, such as natural earth colors, siennas and ocres. Titanium, carbon and ultramarine pigments also belong to this category, as well as cobalt and cadmium. Many of these pigments are now also manufactured synthetically. Organic pigments have their origins in the 19th century. Industrial production developed at the beginning of the twentieth century owing to new manufacturing processes in organic chemistry. These synthetic pigments have become an important group in the manufacture of artists’ colors, producing bright and luminous shades of great intensity and excellent light fastness and permanence. The range has extended continuously, and now besides the familiar phtalocyanines and naphthols, includes azo compounds, dioxacines and pyrroles, antraquiniones and quinacridones.